It is desirable to detect plaque deposits in the oral cavity to direct action for removal, for example by using toothbrushes (manual or power), tooth floss, tooth picks, or oral irrigators, as detection indicates the areas at which dental cleaning effort should be focused. Such deposits can be difficult to detect in situ/in vivo on the teeth, gums, tongue, or cheek. It is especially important to detect dental plaque. For detection of dental plaque it is known to use fluorescence measurement, in which incident radiation is directed at the surfaces of the oral cavity, and fluorescence radiation having characteristics associated with the presence of biological deposits is emitted from the surfaces and is detected.
In the state of the art there are two general methods for detecting dental plaque. One method uses primary fluorescence, where the fluorescence of dental plaque or other dental material itself is monitored. The other method uses secondary fluorescence, where surfaces in the oral cavity suspected of bearing dental plaque are treated with a fluorescent label material which preferentially binds to dental plaque, and the fluorescence emission of the label material on the oral cavity surfaces to which it has bound is detected to indicate the presence of dental plaque.
In accordance with the foregoing, apparatuses configured for detecting dental plaque sometimes utilizes monochromatic light to illuminate a potential dental plaque site. In certain instances, the site may be illuminated by a light having a predetermined wavelength or range. Other methods and/or apparatuses may utilize a fast excitation pulse (e.g., nanosecond or faster) and fast and sensitive detection devices that are enabled (e.g., gated) at very short time intervals after the excitation pulse. Such methods and/or apparatuses, typically, utilize photomultiplier tubes, avalanche photodiodes and/or Kerr-gates.
While the aforementioned methods and apparatuses are suitable for detecting dental plaque, such methods and apparatuses are generally expensive and include components that are, typically, bulky and require high voltages.
In addition, the aforementioned methods may use one or more calibration methods, e.g., priori knowledge of plaque and background fluorescence lifetimes. For example, one known method uses calibration on a clean enamel site. These methods, however, do not account for variation in background fluorescence within each individual, nor does these methods account for variations in the fluorescence lifetime of different plaque cultures.